This invention relates to copy protection of recording data in a disk recording/reproducing system (medium, recording apparatus, reproducing apparatus).
Further, this invention relates to copy protection for a data recording medium which requires a dishonest copy preventing process for protection of copyright or the like.
Further, this invention relates to copy protection for a reproducing apparatus for reproducing data from a data recording medium such as an optical disk by use of convergent light obtained by converging a laser beam.
Conventionally, copy protection techniques have been used for protecting the copyright of video software or the like. As a typical example of software which requires copy protection, a DVD video disk and DVD-ROM disk using a digital recording system are provided (DVD is an abbreviation for a digital video disk or digital versatile disk). Conventionally, encryption has been used for copy protection of digital recording video software.
The copy protection method using encryption is effective in DVD video disk or DVD-ROM disk in which encrypted data is recorded. However, in the case of a DVD-RAM in which the user can newly record data, the following problems occur.
(1) It is difficult to manage an encryption key necessary at the time of encryption.
(2) It is difficult to attain a strong encryption process for a disk recording/reproducing apparatus (such as a DVD-RAM recorder that effectuates digital recording and reproducing processes similar to an analog video cassette recorder under the control of a user. In addition, the encryption process may easily be deciphered.
(3) In a case where the encrypting and decrypting processes occur in a disk recording/reproducing apparatus, a copy of the data content to be protected from being copied can be made by decrypting data that is formed and encrypted using another disk recording/reproducing apparatus and encrypting the data again.
Accordingly, when the above recording/reproducing apparatus of digital video data is used, it is difficult to attain an effective copy protecting process using the above encryption technique.
Further, improving the copy protecting process by using an independent method for the DVD-RAM data recording medium complicates the copy protection processing circuit when the data recording medium is reproduced by a DVD-ROM driver or when the DVD-ROM disk is reproduced by a DVD-RAM driver, increasing the production costs of the DVD-RAM and DVD-RAM drivers.
A copy protection system that prevents unauthorized copying of a recordable digital data recording medium, such as a DVD-RAM disk, is disclosed and can be used with various data recording mediums that contain reproduction-only data recording media.
The disclosed invention is a copy protecting method for an optical medium that writes watermark data, such as error correction control (ECC) data, to a data storage area of a disk.
The disclosed invention further comprises a step of extracting the watermark data from ECC data on the disk and comparing the extracted watermark data with collation data to determine the validity of the disk based on the result of the comparison.
The following example describes the method and system of the present invention. Consider a case where a party wants to copy dishonestly a disk onto another disk using separately a disk reproducing apparatus and a disk recording apparatus that receives an output from the disk reproducing apparatus. When the party loads the disk into the reproducing apparatus that reads the disk, storage data such as video image data is output from the disk and the reproducing apparatus. Watermark data and error correction data is eliminated, however, by an error correction circuit in the reproducing apparatus. Accordingly, the disk storage data having the eliminated electronic watermark data is output from the reproducing apparatus to the recording apparatus, and the recording apparatus records the storage data without the electronic watermark data into a new disk.
When the new disk is read by a reproducing apparatus having an electronic watermark collating function, the electronic watermark cannot be extracted, the collating function cannot be performed, and the disk is detected as an invalid disk. Thus, a copy-protected disk that prevents dishonest copying by a normal disk reproducing apparatus and a normal disk recording apparatus is attained.
The copy protecting method of this invention eliminates the electronic watermark data at the time of dishonest copying by use of the error correction circuit that is provided in a DVD reproducing apparatus.
Further, the present invention includes an optical medium having a data storage area provided on an optical disk that stores digital data and a plurality of ECC blocks that store watermark data as ECC data together with other certain data.
The present invention describes a disk that stores electronic watermark data used in the copy protecting method. The electronic watermark data is stored as ECC data in each ECC block of the data storage area and is read out and compared with collation data in the reproducing apparatus. If a similarity of certain level or higher level is attained between the electronic watermark and collation data, the disk is determined to be a valid disk. If the similarity of certain level cannot be detected, however, the disk is determined to be an invalid disk, an error message is displayed to a user, and disk reproduction is interrupted.
Further, the present invention comprises an optical disk reproducing apparatus having an extracting means for extracting watermark data from ECC data stored in a storage area of the optical disk in which the watermark data is stored as the ECC data.
The present invention compares the extracted watermark data with the collation data to determine a validity of the disk based on a result of the comparison, eliminates the error data and watermark data from the certain data based on the ECC data, and outputs the certain data.
The present invention further describes the electronic watermark data collating function of the reproducing apparatus for protection from dishonest copying. The electronic watermark data, stored as the ECC data, is extracted by the reproducing apparatus and is compared and collated with collation data stored in part of a recording area of the disk. If a similarity of certain level or higher level is attained between the electronic watermark data and collation data, the disk is determined to be a valid disk having the electronic watermark. Otherwise, the disk is determined to be an invalid disk.
Since the electronic watermark data is eliminated as ECC data by the error correction circuit after the collating process, image data or the like can be recorded if an output of the reproducing apparatus is connected to an input of the recording apparatus to copy dishonestly the disk into a new disk. All of the data containing the electronic watermark data, however, cannot be copied. Accordingly, the error correction circuit of the reproducing apparatus provides the copy protection of the present invention.
Additional objects and advantages of the invention are set forth in the description that follows, and in part are obvious from the description or may be learned by practice of the invention. The objects and advantages of the invention are realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.